Atrial myocytes are continuously exposed to shear stress during cardiac cycles. Previous reports have shown that shear stress induces two different types of global Ca2+ signaling in atrial myocytes-longitudinal Ca2+ waves (L-waves) and action potential-involved transverse waves (T-waves), and suggested an underlying role of the autocrine activation of P2 receptors. We explored the correlations between ATP release and Ca2+ wave generation in atrial myocytes and investigated why the cells develop two Ca2+-wave types during the same shear force. We examined whether ATP release correlates with different shear-stress (~16 dyn/cm2)-mediated Ca2+ signaling by simultaneous measurement of local Ca2+ and ATP release in individual atrial myocytes using two-dimensional confocal imaging and sniffer patch techniques, respectively. Functional P2X7-receptor-expressing HEK293 cells were established as sniffer cells, which generated currents in real time in response to ATP released from a closely positioned atrial myocyte. Both shear-stress-induced L- and T-waves were preceded by sniffer currents with no difference in the current magnitude. Left atrial (LA) myocytes had two- to three-fold larger sniffer currents than right atrial (RA) cells, as was confirmed by ATP chemiluminescence assay. Shear-stress-induced ATP release was eliminated by connexin (Cx) 43 hemichannel inhibition using La3+, Gap19, or knock-down of Cx43 expression. The level of phosphorylated Cx43 at Ser386 (p-Cx43Ser368), but not total Cx43, was higher in LA versus RA myocytes. Most LA cells (~70%) developed L-waves, whereas most RA myocytes (~80%) presented T-waves. Shear-stress-induced T-waves were completely removed by inhibition of P2X4R, which were most abundant in rat atrial cells. Expression of P2X4R was higher in RA than LA myocytes, whereas expression of P2Y1R, the mediator of L-waves, was higher in LA than RA myocytes. ATP release mainly triggers L-waves in LA myocytes and T-waves in RA myocytes under the same shear force, partly because of the differential expression of P2Y1R and P2X4R between LA and RA myocytes. Higher ATP release in LA myocytes under shear stress may not contribute to determination of the wave pattern.

中文翻译：

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左右心房肌细胞中不同剪切诱导的Ca2 +信号传导：P2受体背景的作用。

在心脏周期中，心房肌细胞不断地承受剪切应力。以前的报道表明，剪切应力在心房肌细胞中诱导了两种不同类型的整体Ca2 +信号传导-纵向Ca2 +波（L波）和动作电位涉及的横向波（T波），并提示了自分泌激活的潜在作用P2受体。我们探讨了心房肌细胞中ATP释放与Ca2 +波生成之间的相关性，并研究了为什么细胞在相同的剪切力下会产生两种Ca2 +波类型。我们通过分别使用二维共聚焦成像和嗅探器贴片技术同时测量单个心房肌细胞的局部Ca2 +和ATP释放，来检查ATP释放是否与不同的切应力（〜16 dyn / cm2）介导的Ca2 +信号传导相关。将表达功能性P2X7受体的HEK293细胞建立为嗅探细胞，该嗅探细胞响应从紧密定位的心房肌细胞释放的ATP实时产生电流。剪应力引起的L波和T波都带有嗅探电流，电流大小没有差别。ATP化学发光分析证实，左房（LA）心肌细胞的嗅探电流比右房（RA）细胞大2至3倍。剪应力诱导的ATP释放被La3 +，Gap19或Cx43表达的抑制通过连接蛋白（Cx）43半通道抑制消除。LA上的Ser386（p-Cx43Ser368）磷酸化Cx43（p-Cx43Ser368）水平高于RA心肌细胞，但不是总Cx43。大多数LA细胞（〜70％）产生L波，而大多数RA心肌细胞（〜80％）呈现T波。剪切应力诱导的T波通过抑制P2X4R而完全消除，P2X4R在大鼠心房细胞中含量最高。RA中P2X4R的表达高于LA心肌细胞，而L波介体P2Y1R的表达在LA高于RA心肌细胞。ATP释放主要在相同的剪切力下触发LA肌细胞的L波和RA肌细胞的T波，部分原因是LA和RA肌细胞之间P2Y1R和P2X4R的差异表达。剪应力作用下，LA心肌细胞中较高的ATP释放可能不会有助于确定波动模式。ATP释放主要在相同的剪切力下触发LA肌细胞的L波和RA肌细胞的T波，部分原因是LA和RA肌细胞之间P2Y1R和P2X4R的差异表达。在剪切应力下，LA心肌细胞中较高的ATP释放可能不会有助于确定波动模式。ATP释放主要在相同的剪切力下触发LA肌细胞的L波和RA肌细胞的T波，部分原因是LA和RA肌细胞之间P2Y1R和P2X4R的差异表达。剪应力作用下，LA心肌细胞中较高的ATP释放可能不会有助于确定波动模式。